Since most states have now adopted a three-letter prefix or suffix for licence plate numbers for private vehicles, you can probably imagine that certain combinations such as FUX, DIK, CUM, ASS, or HOR are outright banned. Other combinations that once meant nothing (such as HIV) have recently been added to many ban lists because of their newly acquired darker meaning. Some combinations with the letter 'Q' get banned, because it looks so much like 'O'. Thus you're unlikely to see CQK, FQK, or HQR
Others are banned on racial or ethnic grounds (JEW, MEX) or are combinations that are considered racial slurs such as JAP or NIG. Others might not be blatently offensive, but are banned because they could cause embarrassment for motorists. Examples include BUM, GOD, DUD and UGH. Still others are not issued because of drug references such as POT or LSD.
Occassioinally, some objectionable combinations slip through and get printed like the infamous issue of the ASS prefix in New Brunswick (which were never distributed and supposed to be destroyed but somehow found their way into private collections) or a case in Ohio a few years ago when the SIN prefix was issued, prompting many outraged motorists to return their plates.
Others may be unique to a particular state. For example, the prefix 'DVN" is banned in Florida, but not California. Conversely. 'SLA' is banned in California but not Florida. California also is unique in banning CHP solely due to its reference to CHiPS - California Highway Patrol - and the confusion that may result in motorists thinking they were cops plates.
Others may find numbers objectionable, particulary 666 for states that still have the three-digit sequences. Motorists turn those in all the time. Or certain combinations of number or letters, harmless on their own, may raise some eyebrows: Ohio is just starting with the Es in their AAA0000 series. I wonder if EAT6969 will be banned or will it slip through. I would love to be at the licence bureau that issues that prefix when those numbers come up.
The links above show a list of banned letter combinations in Florida and California (some of which are no longer banned) Most other states probably have a very similar list. What is mystifying to me is why combinations like CUZ, EEK, FAN, QVA, SAM, or YEP. CUZ is a recent add, one of four to be added since 1979. Are these combinations blatetently offensive for some reason?
And SAC! California has banned the prefix SAC for some reason. Anyone know why?
Excluding vanity plates, have you ever seen any strange letter combinations that got issued in your state or province?